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Infection and Immunity, February 1999, p. 546-553, Vol. 67, No. 2
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

The Link between Phylogeny and Virulence in Escherichia coli Extraintestinal Infectiondagger

Bertrand Picard,1 José Sevali Garcia,2 Stéphanie Gouriou,1 Patrick Duriez,3 Naïma Brahimi,4 Edouard Bingen,4 Jacques Elion,3 and Erick Denamur3,*

Laboratoire de Microbiologie, Hôpital Morvan, Brest,1 Laboratoire de Microbiologie, Hôpital Cochin, Assistance Publique---Hôpitaux de Paris,2 INSERM U 4583 and Laboratoire de Recherche en Bactériologie Pédiatrique (JE 2255), Université Denis Diderot-Paris 7,4 Hôpital Robert Debré, Paris, France

Received 27 April 1998/Returned for modification 13 July 1998/Accepted 5 November 1998

Previous studies suggesting a link between Escherichia coli phylogenetic groups and extraintestinal virulence have been hampered by the difficulty in establishing the intrinsic virulence of a bacterial strain. Indeed, unidentified virulence factors do exist, and the susceptibility of the host to infection is highly variable. To overcome these difficulties, we have developed a mouse model of extraintestinal virulence to test the virulence of the strains under normalized conditions. We then assessed the phylogenetic relationships compared to the E. coli reference (ECOR) collection, the presence of several known virulence determinants, and the lethality to mice of 82 human adult E. coli strains isolated from normal feces and during the course of extraintestinal infections. Commensal strains belong mainly to phylogenetic groups A and B1, are devoid of virulence determinants, and do not kill the mice. Strains exhibiting the same characteristics as the commensal strains can be isolated under pathogenic conditions, thus indicating the role of host-dependent factors, such as susceptibility linked to underlying disease, in the development of infection. Some strains of phylogenetic groups A, B1, and D are able to kill the mice, their virulence being most often correlated with the presence of virulence determinants. Lastly, strains of the B2 phylogenetic group represent a divergent lineage of highly virulent strains which kill the mice at high frequency and possess the highest level of virulence determinants. The observed link between virulence and phylogeny could correspond to the necessity of virulence determinants in a genetic background that is adequate for the emergence of a virulent clone, an expression of the interdependency of pathogenicity and metabolic activities in pathogenic bacteria.


* Corresponding author. Mailing address: INSERM U 458, Hôpital Robert Debré, 48 blvd. Sérurier, 75395 Paris cedex 19, France. Phone: 33 140 03 19 31. Fax: 33 1 40 03 22 77. E-mail: denamur{at}infobiogen.fr.

dagger This paper is dedicated to the memory of Philippe Goullet, a pioneer in the analysis of the genetic structure of E. coli.


Infection and Immunity, February 1999, p. 546-553, Vol. 67, No. 2
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.



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